The Atlas V launch vehicle currently handles most national security missions. (Lockheed Martin)

The Air Force this week opened competition for a national security space launch for the first time in a decade.

The service on Tuesday released a request for proposal from industry for the procurement of a National Security Space mission in 2016. This would be the first Evolved Expendable Launch Vehicle competition in a decade and “a significant milestone in the Air Force’s efforts to bring competition into the EELV program,” Air Force spokeswoman Capt. Erika Yepsen said in a statement.

“Competition among certified launch providers will encourage innovation and continued cost savings, while ensuring the Air Force will continue its focus on mission success,” Yepsen said.

The service did not release any details on the launch payload or possible cost.

The announcement comes after a long public battle between the Air Force and new competitor SpaceX, which filed a lawsuit in the U.S. Court of Federal Claims after the service announced a sole-source block buy of 36 launches from United Launch Alliance, a Boeing-Lockheed Martin joint venture. The service had set aside a smaller amount of launches, up to eight, for competition.

“Essentially what we feel is ... that the national security launches should be put up for competition and they should not be awarded in a sole-source, uncompeted basis,” SpaceX CEO Elon Musk said when he announced the lawsuit in April.

At the same time, a judge issued an injunction against the purchase of the Russian-made RD-180 rocket engine that is used by United Launch Alliance in its Atlas V vehicle, which handles most of the national security missions. The injunction was lifted in May, with the judge stating that the purchase of RD-180s does not directly benefit Russian Deputy Prime Minister Dmitry Rogozin, one of multiple Russian officials sanctioned by the U.S. Treasury Department in response to the conflict in Ukraine.

Musk said last month that SpaceX is on track for its Falcon 9 rocket to be certified for military launches before the end of the year.

The United Launch Alliance’s use of the Russian-made engine in the Delta V has become a political issue, with Congress grilling service leaders on possible plans to replace the engine and move forward with national security launches that do not involve Russian-made components. The announcement for the EELV proposal came during a joint hearing Wednesday before the Senate Armed Services and Commerce, Science and Transportation committees.

During the hearing, Gen. William Shelton, commander of Air Force Space Command, said if the Defense Department is forced to move ahead on space launches without the Russian engine, it could lead to a slip of between 12 months and 20 months for most missions, and up to 48 months for heavier missions that require the use of the Atlas V.

The delay could put satellite constellations at risk, Shelton said.

“It is dire,” he said.

The U.S. has a stockpile of 15 engines remaining, and the time line for future launches would depend on how the services decides to allocate them.

In the meantime, the Space X certification decision later this year could help the service move forward, though there are limitations. The current Atlas V has 10 different configurations that would allow the service to launch different payloads into space, with Space X only able to meet three of those configurations, Shelton said. And while SpaceX does have a heavy vehicle planned, the Falcon Heavy, it is “down the road a ways.”